Steps to replicate the issue (include links if applicable):

• Visit a large article, e.g. https://en.wikipedia.org/wiki/Barack_Obama (this is only needed to make sure the loading of VE is relatively slow)
• Click "Edit" to enter VisualEditor
• While VisualEditor is loading click "Read" or "Article" or use the browser-navigation to go back or press ESC

What happens?:

The VE UI looks like it's canceled, and the URL updates to a non-editing URL... but then VisualEditor loads or partially loads (e.g. the toolbar appearing above the non-editable read-mode of the article, with the editable surface below it).

If back is hit *really* quickly, VE will load fully and then exiting to read mode will take you back to something that looks like read mode but has an editing URL.

What should have happened instead?:

VisualEditor should be completely exited, as it would if you waited for the load to finish and then exited it using any of the listed methods